Variable inductance coil



2 Sheets-Sheet l Feb 24, 1925.

R. E. MBCDOWELL VARIABLE INDUCTANGE COIL Filed May 18, 1925 Feb. 24,1925. 1,527,484

R. E. MacDowl-:LL

VARIABLE INDUCTANCE COIL FiledA May 18, 1923 2 Sheets-Sheet 2 I ozb?. ,3

V/Zf,

i: mmm

I vemar Patented Feb. 24, 1925.

UNITED STATES PATENT OFFICE.

ROBERT E. MAODOWELL, OF CLEVELAND, OHIO, ASSIGNOR TO THE WOR-KRITE MANUAFACTURING COMPANY, OF CLEVELAND, OHIO, A CORPORATION.

VARIABLE INDUCTANCE COIL.

Application filed May 18,

T 0 all whom t may concern:

Be it known that I, ROBERT E. MAoDow- ELL, a citizen of the UnitedStates, residing at Cleveland, in the county of Cuyahoga and State ofOhio, have invented certain new and useful Improvements in VariableInductance Coils, of which the following is a specification.

This invention relates to inductance coils and has particular referenceto an improved form of variable inductance coil for use in radiocircuits.

Heretofore it has been customary to vary the number of turns of wire ofan inductance coil either by providing a movable contact finger orslider which is movable along the coil to engage separate turns of thewire, or by tapping the coil at certain definite intervals andconnecting each tapI with one of a series of contact points over which aswitch arm is movable to vary the number of turns in the circuit. Thesearrangements are each open to many objections, the most important ofwhich is that the unused portion 'of the coil is always connected withthe circuit and hence absorbs energy. This loss of energy is usuallyreferred to as dead end loss and becomes an important factor i in radiocircuits wherein the currents handled are of a very small value and eachinstrument must be designed and constructed for maximum efficiency,

It is the general object of the present invention to provide an improvedmanner of varying the number of turns of an inductance coil wherein theunused portion of the unit as a whole, greatly increased.

Another object is to provide an improved manner of varying the number ofturns of an inductance coil which sha-ll be applicable with equalsuccess to stationary or stator windings, and to movable or rotorwindings.

Another object is to provide an inductance coil of the aforesaidcharacter wherein the inductance may be varied progressively by smallvalues.

A further object of the invention is to permit 100% inductiverelationship by bringing portion of coil in use in a direct inductivecouple.

1923. Serial No. 638,862.

A still further obj ect is to provide an improved inductance unit whichshall be simple in construction, easy to operate, and which shall beinexpensive to manufacture.

lVith these and other objects in view, the invention consists in thevarious novel features of construction and arrangement or combination,all of which will be fully described hereinafter and pointed out in theappended claims.

In the accompanying drawings wherein I have shown certain illustrativeembodiments of my invention but without intent to limit myself thereto,Fig. 1 is a vertical sectional view through a portion of a variocoupleremploying my invention; Fig. 2 is a sectional view taken on the line 2 2of Fig. 1; Fig. 3 is a vertical sectional view through the rotor of theinductance unit; and Fig. t is a similar view taken at right angles toFig 3.

Describing by reference ycharacters the various parts illustrated 1denotes a suitable insulated form over which the stator winding 2 of theinductance unit is wound. This form is preferably spherical in shape sothat the rotorI winding, to be referred to more fully hereinafter, maybe varied with respect to the stator winding by means of a rotary motionand thus occupy a minimum space. Rising from the form 1 is asubstantially rectangular housing 3 also formed from insulating materialand the upper end of this housing is normally closed by means of a. capl which is conveniently secured thereto at each side by a. binding post5. coil shall be eliminated from the circuit and hence the aforesaiddead end'losses shall be avoided and the efficiency of the inductanceJournalled within the housing are a pair of shafts 6 which are arrangedin spaced parallel relation and each shaft has mounted thereon a pawl 7.These pawls are each provided with suitable gear teeth 8 which areintermeshed so that movement of one pawl will cause a correspondingmovement of the other in a reverse direction. One of the shafts 6 alsohas mounted thereon a segmental gear 9 which is pinned to the pawl asindicated at 10. This gear is ineshed with a pinion 11 which is mountedon a shaft 12 that 'is journalled in the cap 4. As shown in F ig. 2,shaft 12 projects through each side of the cap and is adapted to receivean operating lever such as a dial (not shown), while the opposite end isreduced Cil and housing is a. fiat or leaf spring 18 which" extendsdownwardly valongeach sideofthe housing and inwardly betnf'eensaidhousing and the stator form 1, and then upwardly into engagement withits respectivepawl' 7.

These metallic springs serve as conductors,

as will be more fully explained hereinafter,

and in order to insure good electrical contact with their respectivebinding posts 5, I preferably surround the stein of each post with ametallic bushing 19 which offers an increased `area 'of contact betweensa'id spring and post.'

In operation, the binding posts are connected in the circuit in anydesired {man-ner, as for example, one to the aerial iand the other tothe ground. Shaft ,12 is Vthen rotated which rotates pinion 11 andsegmental gear 9 and this inlturn rotates the pawls 7 in oppositedirections which serves to urge the fiat 'springs 18 progressively intolcontact with the previously bared turns of the stator .vinding.V It'will be obvious that'the springs contacting withthe stator winding willshort circuit the turns thereof with which they are in contact and hencethese unused turns will Vin :effect be eliminated from the cicuit as adirect electrical path will be provided, through thel medium of thesprings, direct to the binding posts. It y'will be 'noted thatthesprings are preferably arranged'so that they -will normally fbein'con# tact with the outer or Tfirst `and last turns of the statorwinding-and in this position maximum inductance will be obtained. Theinductance is gradually reduced as the springs progressively shortcircuit the turns of the winding and minimum inductance is obtainedwhenthe springs are in contact along their entireV length with thepreviously fbared paths on the stator winding In Figs. 3 and t Ihaveshown my invention applied to a movable or rotary winding. In theseviews, 25 denotes the rotor form which is made of a suitable insulatingmaterial and is provided with a winding 26. A hollow shaft or'sleeve 27is secured to and projects from Vdiametrically opposite points of therotor form, and these sleeves `serve as axes about which the. rotorrevolves with respect to the stator winding to vary Vthe couplingbetween these windings. *One of these sleeves is preferably projectedbeyond thev stator form so that ali-operating handle such as a dial'(not shown) maybe conveniently applied thereto. Journalledwit-hin'each'sleeve 27 is a shaftv 28,and the inner opposing ends ofthese shafts are connected by means of Van insulatingftube 29 so thatrotation of one of said shafts will cause a corresponding movement ofthe anglesthereto sol that said fingers lie in the saine' planeofrotation. The outer end-"of each iingeris bent to defin'eacontact shoe3Q which is in the shape of a segment of a circleV andthes'e shoesextend in opposite directions as clearly shown in Fig. 3. The shoesareadapted'to'move thro-ugh diametrically opposite slots 33 formed inthe rotor and thus contact progressively with the iniV ner surface ofthe previously bared turn'sof wire forming the rotor'w'inding. In'thismanner theftur'ns of the rotorl windingare progressively short circuitedfrom the outer edges rtoward the-center and hence a direct' electricalcircuitv is obtained through the contact lingers andrespectiveshafts-andthe short 'circuitedl' 4turns or 'unused portion? ofthe Winding .is eliminated Jfrom' the circuit.

In some instances it might be desirablej'to have both the primary orstator'winding andthe secondary or rotor ,winding variable, while inother'instances it might be desir able to haveV only the Ystatoror onlyvthe rotor winding variable and such modifications are deemed'w'ithintlie'scope'of the presentinvention. Y

While I havesliown and, described my in{ vention as applied' to whatV4is commonly known as a variocoupler, it will be under# stoodthatit'm'ay be applied with equal success to variometers or other formof inductance units employingv a single coil or j posite ends thereoftoward the middle, to

short circuit successive turns in said sections, and means foroperating?vv said' conv tacts simultaneously andA uniformly.-

2. VThe combination Awith an" inductance coil, of la pair of conductorsarranged one 'adjacent eachend of the coil,and means for placing saidconductors into contact with the l Vcoil toshort circuit succeedingturns from oppositev ends thereof, -to vary the inducta'nce'of the coilf3.* The combination with an inductance -coil,'of a. pair-of conductorsarranged one adj acent' eachend of the coil, andl meansY for s1multaneously v'placing saldconductors yinto contact. with the coil toshort circuit succeeding turns from opposite ends`thereof, to varythenductance of the coil.

4f. The combination with anfinductance coil, of a pair of conductorsarranged one adjacent each end of the coil, a shaft1 and meansconnecting said shaft Witheach of said conductors whereby rotation ofthe former will urge the latter simultaneously into Contact withsucceeding turns of the coil from opposite ends thereof, to Vary theinduetance thereof.

5. The combination with an inductance ooil7 of a pair of conductorsarranged adjacent each end of the coil, a shaft and a pawl connected toeach of said conductors and to said shaft whereby rotation of said of acoil wrapped around said surface and defining a segment of a sphere,flexible strip conductors adapted to engage successive turns of the coilfrom opposite ends thereof7 said strip conductors being adapted touniformly short circuit successive turns of the coil from the endstoward the middle of the winding, and means for operating said stripconductors simultaneously and uniformly.

In testimony whereof I affix my signature in presence of two witnesses.

ROBERT E. MACDOWELL.

Witnesses:

B. VHITLEY, H. RODINE.

